Measuring global position using the Sun

The determination of latitude and longitude on Earth has always been of interest to explorers and cartographers alike. Accurate positional information is often needed for rescue purposes in locations where satellite navigational systems are inoperable. The activity described in this paper demonstrates a simple procedure to determine latitude and longitude using a structure that casts a shadow and a clock. The latitude is calculated by the angle of the shadow cast by the midday Sun, and the longitude determined by knowing the local noon time in terms of the universal time. Using this technique, the latitude is usually within 1.5° of the true value, whilst the longitude within 0.25°. This exercise would be suitable as a high-school class experiment.